Magnetic powder scavenging arrangement

ABSTRACT

A device for scavenging magnetizable powder from e. g. a drum in a printing apparatus. The powder is attracted from the drum to the surface of a nonmagnetic tube positioned parallel to the drum, which has contained therein a rotatable set of adjacent bar magnets. The rotation of the magnets causes, via the bar magnets&#39;&#39; divergent magnetic flux field, the attracted powder to work its way around the surface of the tube in opposite direction to the magnet rotation and onto a ledge extension of the tube surface. The powder eventually is moved sufficiently distant from the field to enable it to fall into a collector trough.

i United States Patent [151 3,659,311 Waren [4 May 2, 1972 54 MAGNETIC POWDER SCAVENGING 3,402,698 9/1968 Kojima et al v.209/219 X ARRANGEMENT 3,152,924 10/1964 Wamelista et al l7/l7.5 X [72] Inventor: Frank Arthur Oakley Waren, l-love, En- P i Examiner-Leon G. Machlin gland AttorneyC. Cornell Remsen, Jr., Walter J. Baum, Paul W, Hemminger, Charles L. Johnson, Jr., Philip M. Bolton, Isidore [73] Asslgneei Creed & Company Sussex England Togut, Edward Goldberg and Menotti J. Lombardi, Jr. [22] Filed: Apr. 22, 1970 211 Appl. No.: 30,730 [57] ABSTRACT A device for scavenging magnetizable powder from e. g. a I 30] Foreign Apphcauon Priority Data drum in a printing apparatus. The powder is attracted from the M y 1969 Great Britain drum to the surface of a nonmagnetic tube positioned parallel to the drum, which has contained therein a rotatable set of ad- Cl /2565, 1185371209315 jacent bar magnets, The rotation of the magnets causes, via f 13/41 2 19/00 the bar magnets divergent magnetic flux field, the attracted [58] Field of Search ..l98/41; 118/639, 637 L0, 623, powder to work its way around the surface of the tube in 1 637; 1 17/38; 146/74 1 3 posite direction to the magnet rotation and onto a ledge exten- [OI/DIG 33 /288 32 2; sion ofthe tube surface. The powder eventually is moved sufficiently distant from the field to enable it to fall into a collector [56] References Cited trough UNITED STATES PATENTS Kaufer et al. ..1 18/639 X 4 Claims, 2 Drawing Figures P'A'TE'NTEDMAY 21912 SHEET 10F 2 F/Gi Agent PATENTEnm 2:972 3,659,311

SHEET 2 [IF 2 I lnvenlor FRANK ARTHUR OAKLEY WARE/V Agent MAGNETIC POWDER SCAVENGING BACKGROUND OF THE INVENTION This invention relates to magnetic printing and/or display devices, and in particular to magnetic powder scavenging apparatus therefor.

Such magnetic devices are well known, and essentially comprise a magnetizable surface, such as the surface of a drum or belt, which is movable relative to a set of recording heads and can be selectively magnetized by the heads in accordance with the matter to be printed or displayed, the surface then being dusted with magnetic powder which adheres to the magnetized regions, thus forming a powder image. The dusted surface may then be used directly for display of the powder image, or it may be used as a printing element for transferring the image to a further surface such as a paper tape or sheet.

In copending US. application, Ser. No. 29,330, filed Mar. 18,1970, we describe apparatus for dusting the magnetizable surface of a magnetic printing and/or display device. The same principle upon which that apparatus was based can be used to scavenge unwanted powder from the magnetizable surface after printing and/or display has been efiected, in readiness for a fresh recording.

SUMMARY OF THE INVENTION According to the present invention there is provided in a magnetic printing and/or display device an arrangement for scavenging magnetic powder from the movable magnetizable surface of the device, the arrangement including a nonmagnetic tube disposed adjacent the magnetizable surface, the axis of the tube being parallel to the surface and perpendicular to its direction of movement, a magnetic rotor inside the tube whose axis is parallel with the tube, the rotor producing a system of magnetic flux at the outer surface of the tube which is divergent in a plane perpendicular to the tube axis, and a nonmagnetic ledge extending substantially tangentially from the outer surface of the tube, the arrangement being such that rotation of the rotor in a given direction causes powder attracted by the rotor from the magnetizable surface to creep around the outer surface of the tube and onto the ledge by somersaulting of the powder as the divergent flux field repeatedly scans the outer surface of the tube, the powder being returned under the influence of gravity from the ledge to a container.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic representation in perspective view of the relevant parts of the magnetic powder scavenging arrangement in a magnetic printing and/or display device according to the invention; and

FIG. 2 is a cross-sectional view of the arrangement of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, which are not to scale, the device includes a drum 1 which is mounted in opposite walls 2 of the device housing for rotation about an axis 3. The cylindrical surface 4 of the drum is magnetizable and constitutes the surface on which matter to be printed and/or displayed is recorded as the drum rotates by a stationary set of recording heads, not shown.

A nonmagnetic tube 5, for example of aluminum, is disposed above and adjacent the drum 1 with its axis parallel to the surface 4 and perpendicular to the direction of movement of the latter. At each end, the tube 5 meets the respective wall 2 so that magnetic powder cannot enter the inside of the tube. A nonmagnetic ledge 6 extends tangentially from the outer surface of the tube 5 and curves downwardly and outwardly so that its free edge hangs clear of the drum 1.

A magnetic rotor 7 is located inside the tube 5 for rotation about an axis 8 parallel with the tube. The rotor may comprise a plurality of mutually parallel bar magnets 9, which are disposed side-by-side with their like poles adjacent, thus effectively fonning a flat rectangular magnet magnetized from edge to edge in a direction perpendicular to its'axis. Each edge of the rotor produces at the outer surface of the tube 5 a system of magnetic flux which is divergent in a planeperpendicular to the tube axis (FIG. 2).

In operation, the drum rotates in the direction of the arrow A, and after display and/or printing of the recorded matter has taken place in the usual way the surface 4 of the drum moves towards the tube 5. The rotor 7 rotates in the direction of arrow B and scavenges the powder 10 still adhering to the surface 4 by attraction onto the tube 5 as the surface 4 moves past the tube. The. arrangement is such that the attracted powder 1 1, according to the principle discussed in the copending application referred to above, creeps around the I outer surface of the tube 5 in the direction of arrow C, i.e. in

the opposite direction to the direction of rotation of the rotor, and onto the ledge 6 as the'flux system repeatedly scans the outer surface of the tube. Then under the influence of gravity the powder slides down the ledge and falls into a trough 12 below the drum. The trough 12 contains the supply of powder used for dusting the drum surface after the matter has been recorded, preferably using the powder applicator described in the copending application mentioned above, and thus the scavenged powder can be reapplied to the drum'surface.

Each grain of powder is held in position on the tube by the attraction of its circumferential neighbors, but to assist somersaulting up the side of the tube it may be necessary artificially to roughen the outer surface. We have found that rubbing the outer surface with a medium grade emery paper gives a suitable surface.

It is to be understood that the foregoing description of specific examples of this invention is not to be considered as a limitation of its scope.

I claim:

1. In a magnetic printing and/or display device, an arrangement for scavenging magnetic powder from the movable magnetizable recording surface of the device, comprising a nonmagnetic tubular element relatively immovably disposed adjacent to the magnetizable surface, the axis of said tubular element being parallel to the magnetizable surface and perpendicular to the direction of movement thereof, a magnetic rotor arranged concentrically within said element, the rotor producing a system of magnetic flux at the outer surface of said nonmagnetic element which is divergent in a plane perpendicular thereto, and a nonmagnetic ledge extension to said tubular element extending substantially tangentially from the outer surface thereof, the arrangement being such that rotation of the rotor in a given direction causes powder attracted by the rotor from the magnetizable recording surface to creep in the opposite direction around the outer surface of said nonmagnetic tubular element and onto said ledge by somersaulting of the powder as the divergent flux field of the rotor repeatedly scans the outer surface of said element, the powder being returned under the influence of gravity from said ledge to a powder reservior.

2. The arrangement according to claim 1 wherein when the magnetizable recording surface is provided by a drum, said nonmagnetic tubular element is disposed above the drum, and said nonmagnetic ledge extension curves downwardly and outwardly from said tubular element so that its free edge hangs clear of the drum.

3. The arrangement according to claim 1 wherein said magnetic rotor is a flat rectangular magnet magnetized from edge to edge in a direction perpendicular to its axis of rotation.

4. The arrangement according to claim 3 wherein the flat rectangular magnet comprises a plurality of mutually parallel bar magnets disposed side-by-side with their like poles adjacent.

a k a- 

1. In a magnetic printing and/or display device, an arrangement for scavenging magnetic powder from the movable magnetizable recording surface of the device, comprising a nonmagnetic tubular element relatively immovably disposed adjacent to the magnetizable surface, the axis of said tubular element being parallel to the magnetizable surface and perpendicular to the direction of movement thereof, a magnetic rotor arranged concentrically within said element, the rotor producing a system of magnetic flux at the outer surface of said nonmagnetic element which is divergent in a plane perpendicular thereto, and a nonmagnetic ledge extension to said tubular element extending substantially tangentially from The outer surface thereof, the arrangement being such that rotation of the rotor in a given direction causes powder attracted by the rotor from the magnetizable recording surface to creep in the opposite direction around the outer surface of said nonmagnetic tubular element and onto said ledge by somersaulting of the powder as the divergent flux field of the rotor repeatedly scans the outer surface of said element, the powder being returned under the influence of gravity from said ledge to a powder reservior.
 2. The arrangement according to claim 1 wherein when the magnetizable recording surface is provided by a drum, said nonmagnetic tubular element is disposed above the drum, and said nonmagnetic ledge extension curves downwardly and outwardly from said tubular element so that its free edge hangs clear of the drum.
 3. The arrangement according to claim 1 wherein said magnetic rotor is a flat rectangular magnet magnetized from edge to edge in a direction perpendicular to its axis of rotation.
 4. The arrangement according to claim 3 wherein the flat rectangular magnet comprises a plurality of mutually parallel bar magnets disposed side-by-side with their like poles adjacent. 